Adjustable crucible former for dental molding flask

ABSTRACT

MOLDING OR CASTING APPARATUS FOR PRODUCING DENTAL INLAYS, CROWNS, AND THE LIKE WHEREIN THE CRUCIBLE FORMER UTILIZED IN CONJUNCTION WITH THE MOLDING FLASK IN MANUALLY ADJUSTABLE SO AS TO PERMIT VARYING OF ITS POSITION AND THE POSITION OF THE WAX PATTERN WITHIN THE MOLDING FLASK.

United States Patent Inventor Robert B.Slansk v [56] References Cited Cicero, Ill. (2517 S. Avers Ave., Chicago, UMTED STATES pATENTS I N g 'fggg 2,425,048 8/1947 Schlesinger l64/376X QJ A 1 n 968 2,858,568 11/1958 Myerson l64/376X 1e 3,322,187 5/1967 Weissman 164/376 Patented June 28, 197] FOREIGN PATENTS 767,218 1/1957 Great Britain 164/34 ADJUSTABLE CRUCIBLE FORMER FOR DENTAL Primary Examiner-J. Spencer Overholser MOLDING FLASK Assistant Examiner.lohn E. Roethel 9 Claims 2 Drawing as. Attorney-Freder1ck J. Krubel 164/34, 249/54 ABSTRACT: Molding or casting apparatus for producing Int. Cl B22c 21/10, dental inlays, crowns, and the like wherein the crucible former B22c 9/04 utilized in conjunction with the molding flask is manually ad- Field of Search l64/34, 35, justable so as to permit varying of its position and the position 374, 376; 249/54; 32/17, 70 0f the wax pattern within the molding flask.

ADJUSTABLE CRUCIBLE FORMER FOR DENTAL MOLDING F LASK This invention relates to apparatus for making dental inlays, crowns or the like out of gold or other material, and, more particularly, to a novel casting or molding flask construction embodying means for adjusting the position of the crucible former and wax pattern carried thereby within the molding flask body.

The present invention is primarily concerned with the provision of apparatus utilized by dentists and dental technicians in producing inlays, crowns, bridges, partial dentures and the like out of gold or other similar materials. Briefly, the casting process generally in widespread use involves the placement of a wax pattern having the same marginal dimensions of the dental inlay, crown or the like to be cast within a flask body. In its assembled condition, the flask body is usually in the form of an open ended cylinder and one end thereof is closed by a generally frustoconically shaped crucible former. The wax pattern is supported on the central apex of the crucible former by means of a wax sprue. The flask body is thereafter filled with liquid investment material which is allowed to set or harden. Once the investment material is sufficiently hardened, the crucible former is removed and the flask is subjected to sufficient heat to cause burning out of the wax pattern and wax sprue leaving a mold cavity and a sprue in the hardened investment material. Molten metal such as gold or the like, is then poured through the sprue into the mold cavity to obtain the desired casting.

It is well known in the dental casting field that the length of the sprue is somewhat critical and has an effect on the efficiency of the casting operation as well as on the dimensional accuracy of the resulting dental casting. Ideally, a sprue length of approximately one-fourth inches is desirable. However, it is equally important in the dental casting operation that the wax pattern by positioned within one-fourth inches from the open end of the flask body whereby the gases fonned during the burning out step of the wax pattern and sprue as well as the gasses formed during the pouring operation of the molten metal are allowed-to readily escape. Except in those rare cases where the wax pattern was of a particular size with reference to the size ofthe flask body and the crucible former, it was virtually impossible, heretofore, to ever achieve both ideal objectives in a single casting operation. Compromises had to be made and thereby the efficiency of the operation and the dimensional accuracy of the metal casting were sacrificed. Either the sprue length had to be made longer than the ideal length of one-fourth inches in order to position thewax pattern within onefourth inches of the flask body end opposite the crucible former or the ideal spacing of the wax pattern from the flask body open end was sacrificed so that a sprue length of one-fourth inches could be used. Furthermore, lengthening of the sprue beyond one-fourth inches involves the exercise ofa high degree of skill on the part bf the dental technician and is tedious and requires delicate hand work which is time-consuming. It is, therefore, a primary object of the present invention to substantially obviate the various shortcomings noted above of prior apparatuses for the production of dental inlays and like articles by providing a molding flask wherein the crucible former is manually adjustable along the longitudinal axis of the flask.

A further object of the invention is to provide a molding or casting flask embodying a manually adjustable crucible former whereby a dental inlay and the like of a great many sizes and shapes can be readily accommodated.

A more specific object is the provision of an open ended casing flask for use by dental technicians wherein the crucible former closing one end of the flask is quickly and easily adjustable within the flask along the longitudinal axis thereof to thereby position the wax pattern within a preselected, ideal distance from one end of the flask and to accomplish such ideal spacing of the wax pattern with a wax sprue of no longer than one-fourth inches.

The foregoing and other. important objectsand desirable features inherent in and encompassed by the invention,

together with its many purposes and uses thereof, will become readily apparent from a reading of the ensuing description in conjunction with the annexed drawings, in which,

FIG. 1 is a vertical sectional view of molding or casting apparatus for producing dental inlays, crowns and the like embodying the invention; and

FIG. 2 is an exploded, perspective view of the components and parts of the casting apparatus.

Referring to the drawings in detail, wherein like reference characters represent like elements throughout the various views, the apparatus embodying the invention is designated generally by reference character 10. The molding or casting apparatus 10 includes a generally cylindrical open ended casting flask 11 which is also referred to as a ring in the dental technician art.

The crucible former, designated generally by reference character 12, has a generally cylindrical body 13 which has a diameter slightly less than the internal diameter of the flask 11, the significance of differences in diameter will become readily apparent hereinafter. The crucible former 12 is also provided with a generally frustoconically shaped tip portion 14 which is integrally formed with the body 13. As best shown in FIG. 1, the crucible former 12 is inwardly formed with a central, longitudinal bore 15 extending from the apex of the tip portion 14. A second bore 16, of smaller diameter than the bore 15, is in alignment with and has one end opening into the bore 15. An annular shoulder 17 is thus fonned at the juncture of the bores 15 and 16, the purpose of which will be explained hereinafter. Extending from the face 18 ofthe crucible former body 13 opposite the tip portion 14 and opening into the second bore 16 is an internally threaded recess 19. The crucible former 12 is also provided with a pair of elongated recesses 20 disposed on respective diametrically opposite sides of the longitudinal axis of the crucible former.

As best shown in FIG. 1, the elongated recesses 20 extend from the face 18 and each recess 20 slidingly receives a respective one of a pair of spaced and parallel guide pins 21. The guide pins 21 are integrally formed or otherwise rigidly fixed to the base 22 of the generally cup-shaped housing member 23. The fit between eachguide pin 21 and the recess 20 associated therewith permits the housing member 23 and the crucible former 12 to move readily with respect to each other along the longitudinal axis of the casting flask 11 but restrained from rotating with respect to each other. It will also be noted that the crucible former body 13 slidingly engages the inner cylindrical surface 24 of the housing member cylindrical wall 25 extending from the base 22. The free edge portion of the cylindrical wall 25 is recessed to provide an annular shoulder 26 and a ringlike surface 27. When the housing member 23 and the casting flask 11 are assembled together, one end of the casting flask 11 is disposed within the recess opening of the housing member 23 with the flask end portion firmly but removably seated upon and in sliding engagement with the annular shoulder 26 and ringlike surface 27, respectively, as shown in FIG. 1.

The base 22 of the housing member 23 is provided with a central aperture 28 therethrough, the defining surface of which serves as a bearing for rotatably supporting a screw assembly 29. The screw assembly 29 is provided with external screw threads 30 which are adapted to engage the internal screw threads of the crucible former recess 19. The lowermost end 31 of the screw assembly 29 as viewed in H6. 1, projects from the housing member 23 and has a shape which is preferably nonround.

The projecting end 31 of the screw assembly 29 is press fit into a central nonround aperture 32 formed through the disclike portion 33 of a cap 34. It is to be understood that any suitable means may be employed for rigidly connecting the cap 34 and screw assembly 29 together for cojoint rotation together and with respect to the housing member 23 and the crucible former 12. The cap 34 is provided with an annular peripheral flange 35 integrally formed with the disclike portion 33, which may be readily and conveniently grasped in order to effect rotation thereof with respect to the housing member 23. From the foregoing, it will also be appreciated that relative longitudinal movement between the housing member 23 and the screw assembly 29 and cap 34 is substan tially prevented. By rotating the cap 34 with respect to the housing member 23, the crucible former 12 is movable along its longitudinal axis with respect to the housing member 23 between two limit positions. One positional limit is established when the base 18 of the crucible former l2 abuts the base 22 of the housing member 23 and the other positional limit is established when the peripheral edge 36 of disc 37 suitably attached to the innermost end of screw assembly engages the annular shoulder 38 formed at the juncture of the bore 16 and the threaded recess 19.

When it is desired to use the apparatus 10, a circular disc 39 is first placed within the bore and caused to seat upon the annular shoulder 17. The disc 39 serves as a closure means for preventing the entrance of wax or other material into the bore 16. The bore 15 is then filled with wax and formed to blend with the outer contour of the crucible former tip portion 14. A wax sprue 41 having the ideal length of approximately onequarter of an inch is formed by the technician and such sprue 41 extends from the wax mass contained in the bore 15. The wax pattern 40 is thus attached to and supported by the wax sprue 41. One end of the casting flask ll, lined with a conventional asbestos linen sleeve 42, is inserted over the assembled wax pattern 40 and caused to frictionally engage the ringlike surface 27 snugly and to bear against the shoulder 26. Thus, a sealed joint is provided between the housing member 23 and one end of the casting flask 11 and the housing member 23 and crucible former 12, in effect, close one end of the casting flask 11 when the components are assembled together in the aforesaid manner. in most instances, the wax pattern 40 will not be positioned within one-quarter of an inch of the open end of the casting flask 11 as desired. Hence, in order to rectify the matter by properly positioning the wax pattern 40 so that it will be disposed approximately one-quarter of an inch from the open end of the assembled casting flask 11, the cap 34 is merely turned in the proper direction with respect to the housing member 23 to effect raising or lowering of the crucible former l2 and, hence, the wax pattern relative to the casting flask 11 until the ideal spacing of the wax pattern 40 from the open end of the casting flask 11 is achieved, Once the wax pattern 40 has been properly positioned, the casting flask 11 is filled with liquid investment matter, indicated by reference character 43, which is allowed to harden or set in a conventional manner. After the investment matter has hardened sufficiently to resist any change in size or shape of the was pattern 40 when handled, the crucible former 12 together with the cap 34 and housing member 23 are stripped from the casting flask 11 prior to transport to conventional casting apparatus (not shown) which forms no part of the present invention for the usual drying out, burning out and casting operations.

It will be appreciated, that stripping of the crucible former 12 is readily accomplished merely by turning the cap 34 slightly in the proper direction to cause the surface area of the crucible former 12 in contact with and somewhat adhesively bonded to the hardened investment material to break away therefrom. Once the adhesive connection or bond between the crucible former l2 and the invention material is broken the crucible former 12, housing member 23 and cap 34 may be readily and bodily moved from the casting flask 11. It will also be noted that inasmuch as the outer diameter of the crucible former body 13 is smaller than the inner diameter of the casting flask 11, as pointed out hereinbefore, the investment material 43 disposed between the crucible former body 13 and the inner surface section of the casting flask ll radially aligned therewith forms, when hardened or set, a smooth entrance lip 44 for facilitating guidance of the molten metal to the mold cavity during the casting operation. it will be noted that, desirably, such entrance lip 44 also extends from the terminal edge of the casting flask 11 so that no portion thereof is exposed directly to the molten casting metal.

lclaim:

1. Apparatus for the'production of dental inlays and the like comprising: casting flask for receiving investment material, said flask being open ended and generally cylindrical in shape; a crucible former disposed within said flask, said crucible former being capable of supporting a wax pattern and a wax sprue on one end thereof, said crucible former having a body cylindrical in shape and having a generally frustoconical tip portion, said crucible former body having a diameter slightly less than the internal diameter of said flask whereby said crucible former substantially closes one end of said flask; and manually operable adjustable means for selectively positioning said crucible former along the longitudinal axis of said flask.

2. Apparatus as set forth in claim 1, including a housing member; means for detachable connecting said housing member to one end of said flask whereby the longitudinal axis of said flask and housing member are substantially in alignment, said housing member being effective to close one end of said flask when connected thereto; and means for operatively connecting said crucible former to said housing member including said manually operable adjustable means for selectively positioning said crucible former along the longitudinal axis of said flask.

3. Apparatus as set forth in claim 2, wherein said housing member is generally cup-shaped in form so as to provide a generally circular base and a cylindrical wall extending from said base; and said means for detachably connecting said housing member to one end of said flask includes an annular shoulder and a ringlike wall surface extending normally from said shoulder, said shoulder and ringlike surface being formed on the free end of said housing member cylindrical wall, one end of said flask being seated upon said shoulder and being frictionally engaged by said ringlike wall surface when said housing member is connected to said one end of said flask.

4. Apparatus as set forth in claim 3, wherein said means for operatively connecting said crucible former to said housing member includes means operatively interconnecting said housing member and crucible former whereby said crucible former and said housing member are constrained from rotating with respect to each other and are capable of moving with respect to each other along the longitudinal axis of said crucible former.

5. Apparatus as set forth in claim 4, wherein said means operatively interconnecting said housing member and said crucible former includes an elongated guide pin, fixed to and projecting from one of said housing member and crucible former, said guide pin being slidable within a recess formed in the other one of said housing member and crucible former, the longitudinal axis of said recess being spaced from and substantially parallel to the longitudinal axis ofsaid crucible former.

6. Apparatus as set forth in claim 5, wherein said manually operable adjustable means for selectively positioning said crucible former along the longitudinal axis of said flask includes a cap mounted on the exterior of said housing member, said cap being rotated with respect to said housing member to effect movement of said crucible former with respect to and along the longitudinal axis of said flask.

7. Apparatus as set forth in claim 6, wherein said manually operable adjustable means for selectively positioning said crucible former along the longitudinal axis of said flask further includes a screw assembly provided with external screw threads and one end rigidly connected to said cap so as to be rotatable therewith and a recess formed in said crucible former having internal screw threads operatively engageable with said external screw threads, said crucible former being movable along the longitudinal axis of said flask between a first position wherein said housing member is closely adjacent to said crucible former and a second position wherein said housing member is longitudinally spaced from said crucible forrner upon rotation of said cap in opposite direction.

8. Apparatus as set forth in claim 7, wherein the longitudinal axis of said screw assembly coincides with the longitudinal axis of said flask, and wherein said crucible former includes a frustoconically shaped tip portion and a generally cylindrically shaped body. The diameter of said body being smaller than the internal diameter of said flask whereby an annular space is provided between said crucible former body and said flask when said flask and housing member are connected together; and wherein stop means are provided for limiting longitudinal movement of said crucible former with respect to said housing member in two directions to establish said first and second positions of said crucible former.

9. Apparatus as set forth in claim 8, wherein said crucible former is provided with a first central bore extending longitudinally from said tip portion, and a second central bore of smaller diameter than and opening into said first central bore, 

